After two days of shuttle diplomacy, Hillary Clinton and Egypt's foreign minister announced a cease-fire agreement between Hamas and Israel. Despite its weakened influence in the Middle East, the US is still the dominant diplomatic force.

The cease-fire, set to take effect later in the evening local time (2 PM EST), would, most urgently, end the rocket fire from Gaza into Israel and the Israeli airstrikes on Gaza, in which more than 140 Palestinians and five Israelis have been killed, most of them civilians.

But at another level, Secretary Clinton’s role in securing the cease-fire demonstrates how the United States, despite its weakened influence in a region of empowered Islamists less inclined to America’s call, remains the dominant diplomatic force in the Middle East.

When President Obama dispatched Clinton to the region Tuesday to try to negotiate an end to the violence, it was a sign of a shift by the White House to a more overt – and traditionally American – role in the region. It was also seen by some regional experts as belated recognition by Mr. Obama that, despite his apparent preference for a less overt role for American diplomacy in the region, the Middle East risks slipping deeper into conflict and instability without forceful US engagement.

Clinton’s apparent success in defusing the Israeli-Palestinian fight could influence how Obama approaches the Syrian conflict, some analysts suggest, if it serves as a reminder that Middle East conflicts often threaten to expand into broader wars if diplomatic efforts – led by the US – don’t intervene first.

That is not to say the challenge Clinton faced from the moment she landed in the region Tuesday was an easy one.

The situation she stepped into in stops in Jerusalem and Ramallah, and on Wednesday in Cairo, presented a Middle East quite different from the one US diplomats, including Clinton, have encountered in recent years and decades.

The changed landscape is one reason an anticipated cease-fire between Israelis and Palestinians fell through Tuesday night.

On Tuesday some Arab diplomats spoke confidently of an impending cease-fire that would allow breathing space for more substantive negotiations on a long-term settlement of issues between Israel and Hamas. But those assertions proved illusory, as Israel appeared to stick to its demands that a “long-term solution” to rocket-fire into southern Israel from Gaza be reached at the outset.

With no agreement in place Wednesday morning, Israeli Prime Minister Benjamin Netanyahu continued to hold out the prospect of launching a ground offensive into Gaza. In the meantime Israel continued to hit targets in Gaza, while rockets continued to sail toward Israeli territory and a bomb exploded on a bus in Tel Aviv.

The agreement Clinton announced Wednesday evening is said to be based on a principle of “quiet in return for quiet,” and a set of “understandings” to reassure the parties about future actions and excpectations.

Clinton encountered a number of changes in the region that made her job tougher, and which will make for a more complex environment for US diplomacy.

Hamas, a militant Islamist organization that the US labels a terrorist group and refuses to engage, finds itself empowered by the rise of Islamist governments in several countries as a result of the Arab Spring. At the same time, US partners in the region that once had working ties with Israel – and which could be counted on to back American diplomatic efforts – have since seen their relations with Israel sour and their sympathies shift.

The Israel-Hamas conflict is also complicated by the involvement of Iran. The Iranian regime’s quest for wider influence in the Middle East in recent years is seen in the longer-range missiles that have been launched in this conflict – toward Tel Aviv, and even to the outskirts of Jerusalem – compared with the rockets in Hamas’s arsenal at the time of a similar conflict four years ago.

The increased range of the rockets – which are fired by a number of extremist groups operating in Gaza, some with close links to Tehran – means that the number of Israelis residing in areas within range of rocket fire has gone up from about a million to about 3.5 million today, according to Israeli officials.

The Sunni Hamas organization is said to have a delicate relationship with Shiite Iran, especially given the increasingly religious fractures in the Syrian civil war – where Iran is backing (and materially aiding) the regime of Bashar al-Assad and his minority Alawite Shiite sect over a rising tide of Sunni Islamist rebels.

President Obama has said that Mr. Assad has lost his legitimacy and must leave power, but the US is also worried that the vacuum left by Assad’s fall might be filled by Sunni Islamists akin to – or perhaps even more extremist than – Hamas.

Such an outcome could potentially pose an even greater threat than Hamas currently does to Israel, the US’s closest ally in the region.

One bright spot from the US perspective in an otherwise damaging conflict is the role Egyptian President Mohammed Morsi has played so far. US officials and some regional experts say they are encouraged by the Islamist leader’s efforts to help reach a cease-fire deal, and how he has refrained from siding too closely with Hamas – even though both Mr. Morsi and Hamas hail from the Muslim brotherhood.

Morsi has limited himself to calling the Israelis the “aggressors” in the fighting – unlike Turkey’s Mr. Erdogan – and has thus preserved a negotiating role from himself and Egypt.

Clinton emphasized Egypt's positive role at the cease-fire announcement, saying, "Egypt is assuming the responsibility and leadership that has long made this country a cornerstone of international peace."